Ice baths kill gains. Does the sauna do the opposite? [New research] — Transcript

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1. 0:00Despite their influencer led popularity, ice bath, cold plunges
2. 0:04and other forms of cryotherapy have been shown quite conclusively in research
3. 0:08to be a net negative for muscle growth and strength development.
4. 0:12They suppress inflammation and slow down chemical reactions.
5. 0:17While lay individuals often think of inflammation as a bad, it's
6. 0:20actually an integral part of the muscle repair process, so suppressing
7. 0:24it has negative consequences for recovery and ultimately, muscular adaptations.
8. 0:28It stands to reason, then, that if cold plunges and all these forms
9. 0:31of cold therapy are bad, is heat therapy actually a positive?
10. 0:35The answer seems to be yes,
11. 0:37according to a preprinted meta analysis of six studies.
12. 0:40The Bayesian analysis
13. 0:41found the 90% probability that heat favored muscle growth.
14. 0:44However, the effect size was very small.
15. 0:47Mechanistically, it's
16. 0:48well established that heat improves the speed of chemical reactions.
17. 0:51It also speeds up blood flow and perhaps most importantly,
18. 0:55very intense heat activates heat shock proteins.
19. 0:58Mild hyperthermia, basically overheating of the body, triggers
20. 1:01a thermo-regulatory response that is not unlike exercise.
21. 1:05It is hormetic.
22. 1:07Hormetic basically means - what doesn't kill you makes you stronger.
23. 1:10So mild overheating triggers adaptive responses
24. 1:13in the body that have some effects, somewhat like exercise.
25. 1:16And they are good for you in small amounts as long as the body can recover
26. 1:20from this.
27. 1:20A 2018 systematic review
28. 1:23concluded that sauna bathing has positive effects on the vascular system.
29. 1:27Moreover, a 2021 meta analysis found that regular sauna bathing
30. 1:31resulted in a clinically meaningful reduction
31. 1:33in blood pressure, namely 4mmHg.
32. 1:37If this sounds too good to be true and you think you can have a nice relaxing
33. 1:40sauna after your workouts, and get better gains
34. 1:42and better health - it is. You need to suffer. Significant heat
35. 1:46stress is required to actually induce the significant health benefits.
36. 1:50For example, a 2026 meta analysis found that regular hot
37. 1:54baths up to 41°C did not significantly improve the vascular system.
38. 2:00The only somewhat meaningful effect was a reduction in heart rate.
39. 2:03So relaxing saunas are not the fountain of youth.
40. 2:05They are also not the ticket to the Olympia.
41. 2:07As I said, the effect size was very small. To quote the researchers,
42. 2:12they named it:
43. 2:12“some evidence of a small effect favoring heat therapy”
44. 2:15and the credible interval extended below zero, which is a statistical way
45. 2:19of saying the actual effect might still very well be zero,
46. 2:23Moreover, for strength development, the effect size was almost exactly zero.
47. 2:26The potential extra
48. 2:27gains are also not free, in the sense that the significant heat stress
49. 2:30that is required to trigger these adaptations might actually delay recovery.
50. 2:34In one of the few studies on elite athletes with a proper placebo control
51. 2:38swimming performance
52. 2:39the day after the sauna was actually impaired.
53. 2:42Many people overestimate how important it is to study trained individuals.
54. 2:45Untrained individuals often have the same effects,
55. 2:47just to a different degree than trained individuals.
56. 2:50However, in the case of the sauna, this might not be true
57. 2:53because if you're already well adapted as an athlete
58. 2:56and your vascular system already has a certain level of adaptation, then
59. 2:59sauna bathing might not be enough stimulus anymore to trigger further adaptations.
60. 3:03Finally, from a health point of view,
61. 3:05sauna bathing is also not completely free from side effects.
62. 3:08It's generally considered quite safe, and it's very self-limiting
63. 3:11in the sense that
64. 3:12most people will not go to the extreme lengths required to actually do damage.
65. 3:16However, it does reduce fertility.
66. 3:18One study concluded sauna use results in a strong impairment of sperm
67. 3:22count and motility, and that was with just two weekly sessions in a Finnish sauna.
68. 3:27The reason is that heat is well established to be toxic to sperm.
69. 3:30This is quite literally why men's balls hang outside of their body.
70. 3:34It's a little bit cooler.
71. 3:35Fortunately, sauna bathing is not strong enough
72. 3:37to do permanent damage to the testes. When you remove the heat stress
73. 3:41sperm quality gradually goes back up to normal levels.
74. 3:44So the reduction in sperm
75. 3:45quality is mostly relevant for people that are right now trying to have kids.
76. 3:49A final significant limitation of the research on heat therapy
77. 3:51is that it's very difficult to have a proper placebo control.
78. 3:54You can't make someone unaware that they're sitting in a sauna,
79. 3:57and many people have positive associations with the sauna,
80. 4:00even if it's just relaxing or health benefits,
81. 4:02and this can result in positive expectation effects, i.e.
82. 4:05the placebo effect,
83. 4:06which makes it very difficult to say if it's just the placebo effect,
84. 4:09or actually the heat stress that triggers these adaptations.
85. 4:12However, considering we have mechanistic evidence linking
86. 4:15the heat stress and the heat shock proteins to the vascular adaptations,
87. 4:18I think it's hard to make this a case for a full placebo effect.
88. 4:22Overall, after reviewing all of the available evidence,
89. 4:25the conclusion I came to in my PT Course is as follows:
90. 4:28If you enjoy sauna bathing or heat therapy, by all means do it.
91. 4:31You probably get some additional health benefits
92. 4:33and it might even slightly improve your gains.
93. 4:36However, if you don't enjoy it, the cost benefit is very poor.
94. 4:40For the time, suffering, and often money that's involved in going to the sauna,
95. 4:43you are much better off exercising.
96. 4:45If you like no nonsense, evidence based
97. 4:47reviews of popular fitness topics,
98. 4:49you'll probably also like this video or check out my PT course.
99. 4:53See you next time!